The invention relates to an endless conveyor for conveying substantially rotationally-symmetrical products, comprising at least one endless conveying element and a number of transverse elements extending substantially perpendicularly to a conveying direction, wherein the endless conveyor comprises a drive mechanism, wherein at least one hourglass-shaped roller is mounted on each transverse element, such that the hourglass-shaped rollers mounted on the transverse elements located one behind the other extend in one or more rows, said rows extending in the conveying direction.
A prior conveyor apparatus is for instance known from U.S. Pat. No. 4,872,564 and is denoted therein by reference numeral 1. In practice, such a conveyor is referred to by the term xe2x80x9croller conveyorxe2x80x9d. The products are nested in the space bounded by two successive rollers of the conveyor. Hence, each roller of the conveyor bounds two nesting spaces. Sometimes, the rollers of the roller conveyor are driven for rotation thereof, causing a product resting on the rollers to rotate as well. This is for instance the case when the product resting on the rollers is to be inspected. In this manner, for instance eggs can be candled and/or checked for breakage in an automatic fashion. Because in general, two products rest on each roller, there is the chance that if one of the products has been fouled, the dirt is transferred from one product onto the other product via the rotating roller. This phenomenon, in practice referred to by the term xe2x80x9csmearingxe2x80x9d, has a consequence that the rollers of the endless conveyor rapidly become foul and that the products located on the conveyor rapidly foul each other. This is highly undesirable. U.S. Pat. No. 2,296,645 discloses a roller conveyor having double rollers. Because in this conveyor, only one product rests on each roller, the problem of smearing is solved. A drawback of this known apparatus, however, is that the diameter of the rollers relative to the products to be conveyed should be relatively small. Indeed, when a larger diameter is selected for the rollers, the center-to-center distance between the successive nesting spaces is particularly large. Such large center-to-center distance is undesirable, since the products are generally supplied in close succession and, accordingly, have to be moved apart in order to be conveyed further via the endless conveyor. Since no special facilities have been arranged for moving the products apart, the products will have to undergo a sudden change of velocity, due to the sudden change of distance relative to each other. After all, if the same amount of products have to be fed through per unit of time, while the products have to be located at a larger distance from each other, this can only be effected by increasing the velocity of the products. The sudden increase of velocity of the products is particularly undesirable, in particular in the case of fragile products, such as for instance eggs. The products may break easily, which leads to fouling of the conveyor and the loss of products.
Another drawback of the conveyor of U.S. Pat. No. 2,296,645 is that the length of the shafts on which the rollers are mounted is limited, as the diameter of these shafts can only be very slight because of the slight diameter of the rollers. The shafts will deflect under the influence of the weight of the products resting thereon, which considerably impedes the operation of the conveyor, in particular in the case of rotating rollers.
An object of the invention is to provide an endless conveyor wherein no smearing occurs and wherein, moreover, no sudden increase of velocity of the products fed thereon occurs.
To this end, according to the invention, the endless conveyor is provided for conveying substantially rotationally-symmetrical products and characterized in that the mutual distance between the successive transverse elements in a first path part is smaller than in a second path part, wherein a first control device is provided effecting an increase of distance between the transverse elements at a first transition from the first to the second path part, wherein a second control device is provided effecting a decrease of distance between the transverse elements at a second transition from the second to the first path part, wherein in at least a portion of the second path part, which portion, viewed in conveying direction, extends from the first transition, a support element has moved between each pair of successive hourglass-shaped rollers for supporting the products to be conveyed.
Such an endless conveyor offers the advantage that the products in the first path part are slightly spaced apart in that, at that location, the mutual distance between the successive transverse elements is less than in the second path part. The products lying against each other that are fed to the endless conveyor are received on the first path part of the endless conveyor. In this first path part, the products are supported by two successive hourglass-shaped rollers. Subsequently, at the first transition, the distance between the hourglass-shaped rollers is increased by means of the second control device. At the same time, a support element is moved between each pair of successive hourglass-shaped rollers, for supporting the products to be conveyed. Hence, after the first transition, the products to be conveyed rest on an hourglass-shaped roller and a support element.
Due to this construction, products are prevented from undergoing a sudden increase of velocity for increasing the mutual distance thereof. After all, the increase of the distance takes place in a controlled manner due to the presence of the control device. The products are already conveyed in a controlled manner in the first path part and at the first transition, the mutual distance between the products is increased in a controlled manner. Hence, the chance of breakage resulting from substantial, suddenly occurring variations of velocity has been minimized, since these variations of velocity do not occur. It is observed that by the term xe2x80x98hourglass-shaped rollerxe2x80x99, any nest-forming element is meant.
To moreover prevent the occurrence of smearing, according to a further elaboration of the invention, the endless conveyor is characterized in that in at least a part of said portion of the second path part, either the hourglass-shaped rollers or the support elements that have moved between the hourglass-shaped rollers are rotatably drivable, while in the first path part, the hourglass-shaped rollers do not rotate.
As a result, no smearing occurs in the first path part, where each hourglass-shaped roller supports two products, because the hourglass-shaped rollers do not rotate there. The hourglass-shaped rollers rotate in the second path part only. However, because in the second path part, each hourglass-shaped roller is in contact with only one product, no smearing can occur between the products relative to each other. Preferably, the distance between the hourglass-shaped rollers in the first path part is so small that the smallest ones of a specific type of product keeps resting on two successive hourglass-shaped rollers, while the distance between the hourglass-shaped rollers in the second path part is so large that the largest ones of said specific type of product can move through two successive hourglass-shaped rollers.